I edit my post on a part of the sea life problems.Not that important, I just but in when I feel I have information that can be relevant. Both the Russian and Swedish fleets are bound to lay up for winter due to ice conditions, and usually, AFAIK, used that time to drydock ships, scrape their bottoms and tar and pitch them. Copper sheeting protects against the shipworm, but another great advantage is that it protects against a lot of sea life (usually of trhe flora kind) that would attach themselves and grow on the hull, slowing the ship down. Copper sheeting was very expensive, if yearly scraping can do the same job, why not use it?
As for the expenses, the Ottomans in the late XVIII could afford it so it was not prohibitively expensive . An additional consideration may be that ships of the Baltic fleet had been rotting: their base was too close to a major river. Anyway, I don’t think that this specific item has any noticeable importance for the TL.
 And after rather foolish experiment of trying to melt the church bells and use their bronze to make cannons, Peter has a huge volume of bronze with which he has no idea what to do.